JK on 40s???

D-Morg

New member
I know this isn't the best overland combination, but I still like my rock crawling....

Who all is running 37+ on their jeeps and atempting overland "style" trips here in the us?

What's your axle combo?

Gas mileage?

Ect?

I'm either looking at a near new JKU Rubicon or a 3rd gen 4runner. I'm a hard core jeep guy so it would be hard for me to change my mind, but I sure am exploring some other directions...

I may just be venting here, but I am having a hard time finding good canidates on craigslist. I am leaning 4runner with 37s on a small lift with some trimming, but I need some motivation to stay on the "dark" side..
 

brianjwilson

Some sort of lost...
You can run 37s on a jk with 2.5-3.5" lift and flat/tube fenders.
If you keep the stock front axle (assuming rubi d44) you'll want to gusset the outer c, install axle sleeves to keep the housing from bending, truss probably, and definitely heavy duty ball joints (synergy or dynatrac). Plus axle shafts front and rear of course. More than 3" of lift is going to require a new front driveshaft. The stock tie rod and track bars are pretty pathetic too. Oh and the steering box. Lol. If you are going to run 37s you'll want to start thinking and hydro assist steering and brake upgrades.

I'm running 35s on my 2012 with 3.5" AEV lift (track bar relocation brackets, drag link flip). So far I've installed a new exhaust y pipe for front drive shaft clearance, a new Tom woods front drive shaft, synergy front track bar, track bar/sector shaft brace, tie rod, ball joints, front axle truss, EVO c gussets and control arm skids. What else.... That mostly it right now, just keep adding things to keep it driving halfway decent on the street and keep from bending things off road. Aside from re-gearing and axle shafts, I probably won't do much else big to the drive train for a while. It is very capable as it is right now with 35s, and really comfortable on the road. Mileage is around 16 town, 18 highway unless I'm doing 80 against the wind, up hill in heavy rain etc. This is with six speed manual and factory 4.10 gears.

I initially planned on flat fenders and 37s but so far I'm glad I didn't. 37s look cool but I don't think it makes sense for me with this vehicle. Like I said its plenty capable for the trails I run, economy is good, braking is decent, and it should be reasonably reliable. I feel like you'll be spending a ton of money to run 37s comfortably and reliably. Doesn't mean you can't, I just think its going to be expensive.
 

marshal

Burrito Enthusiast
to do 40's correctly, you'll need to also set aside roughly $15,000 for a pair of new axles too. 37s are expensive to do, 40s are just plain nuts.

35" tires are the BEST option for an overland JK. you wont stress parts too much and tires are cheaper and easier to find, all the while maintaing decent fuel economy.
 

Septu

Explorer
Pretty much it's all been said above. There's a huge difference in costs to go above a 35" tire, just to ensure that you're not breaking stuff.
 

Bubblegoose1

@PNWINFERNOPRO
38 KM2s, driven daily. Lov'em. Would never go smaller than a 37, for the type of terrain in the PNW.

Also ran 40 MTRs for 2 years, including running the Rubicon, with zero issues. 40s can be done with a few, regular upgrades and a smart gas pedal.
 

Rynomar

Observer
I have been running 37" MTR's on my JK for the last year and love them. I have a '12 with the 6 speed and 4.10's at the moment. I have also put about 3,000 miles on a set of 35's and for everything other than driving on the highway, I really like the 37's a lot more. I have the 3.5" AEV lift with factory fenders. I have done a bit of trimming and adjusting to get them to fit without rubbing, but it is a daily driver and I prefer to have it a little lower. A PR 44 is going to be getting dropped in in the next couple months, but the factory 44 has held up just fine for me so far. I just know its limitations and don't want to have to worry about it any longer. I generally average 16.5 mpg with a light foot of mixed city and highway driving. With the 35's I was consistently getting 19.5.

I think the 35's do make a lot more sense as far as durability, drivetrain life, price, and mpg, but I am sticking with 37's. :) I say go for what you like. Larger tires are going to cost more in several ways, but building it the way you want it the first time is waay cheaper than going back to do it a second time.

Lupe Snow.JPGRIver1.JPG
 

D-Morg

New member
I'm kicking around the idea of getting a base model JK and throwing an Atlas and dana 60's under it already...
 

marshal

Burrito Enthusiast
Just recognize the difficulty of sourcing 40" tires if needed

If you could get 60s in SAE 10 lug, you could run 20" HMETT beadlocks and surplus 42" Michelin XLs. Those are easy to come by surprisingly.
 

Inline6

Adventurer
I'm running 37s and think they would be a good choice for the long wheel base of the 4 door.

If your staying under37s thinking a rubi is a good choice. If 40s I agree get a sport and some bolt in axles. I almost went that way.

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BlueGerbil

C´est le gerbil plus bleu
The JKs from Matthias Jeschke which should drive from Paris via the Bering Strait (where they are right now) to NewYork - 40" MTRs, Dynatrac Pro Rock 60 f+r:

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Here while testing the swimming system:

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onebadtj

New member
I run 40" Trepador radials with a Dynatrac FF 60 rear and a ProRock 60 front. We did a 7 day trip in CO/UT this summer in it. As far as mileage, the JK has a 6.1 Hemi and 5:38 gears. If I'm running on the hwy I can get 15 mpg and city is 8-10 depending on how much fun I'm having. The Jeep did very well I'm Moab for a Jeep this heavy. Hope this helps.

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DE
 
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